Nitrofuryl-triazolo{8 4,3b{9 pyridazine-amide compounds and bacteriostatic compositions

ABSTRACT

WHEREIN R1 is hydrogen or a saturated or unsaturated aliphatic hydrocarbon radical containing 2 to 5 carbon atoms, ARE OUTSTANDINGLY EFFECTIVE AS BACTERIOSTATS AND ARE PARTICULARLY USEFUL IN THE TREATMENT OF BACTERIAL INFECTIONS IN THE URINARY TRACT. Nitrofuryl-triazolo(4,3-b)pyridazine-amide compounds of the formula:

'United States Patent [1 1 Berger et a].

[ 51 Sept. 2, 1975 [73] Assignee: Boehringer Mannheim G.m.b.H.,

Mannheim, Germany [22] Filed: Dec. 18, 1972 [2]] Appl. No.: 316,198

[30] Foreign Application Priority Data Jan. 2l, I972 Germany 2202744[52] US. Cl 260/250 AC; 260/250 A; 424/251 [51] Int. Cl. C07D 237/00[58] Field of Search 260/250 A, 250 AC [56] References Cited UNITEDSTATES PATENTS 3,l38.593 6/l964 Burch 260/250 A 3,483,193 l2/l969 Gull2.60/250 AC 3,506,656 4/1970 Berger et al 260/250 AC 3,522,256 7/l970Berger Cl ill 260/250 AC Primary li.\'unz inerDonald G Daus AssistantExaminer-David E. Wheeler Attorney, Agent, or Firm-Burgess, Dinklage &Sprung ABSTRACT Nitrofuryl-triazolo[4,3-b]pyridazine-amide compounds ofthe formula:

CO-NH-R wherein R, is hydrogen or a saturated or unsaturated aliphatichydrocarbon radical containing 2 to 5 carbon atoms,

are outstandingly effective as bacteriostats and are particularly usefulin the treatment of bacterial infections in the urinary tract.

8 Claims, N0 Drawings NlTROFURYL-TRIAZOLO(4,3-b)PYRIDAZINE- AMIDECOMPOUNDS AND BACTERIOSTATIC COMPOSITIONS The present invention isconcerned with new nitrofuryl-triazolol4.3-b1pyridazine-amide compoundsand with bacteriostatic compositions containing them.

The new nitrofuryl-triazolo[4.3-blpyridazine-amide derivatives accordingto the present invention are compounds of the formula:

l N 11 l wherein R is hydrogen or a saturated or unsaturated aliphatichydrocarbon radical containing 2 to carbon atoms, Thus. R can be alkyl.alkenyl. alkynyl of from 2 to 5 carbon atoms.

We have found that the new compounds (I) according to the presentinvention have surprisingly high antibacterial activity in the urine andare. therefore, especially well-suited for the treatment of infectionsof the urinary tract. Some of the new compounds (I) show. in vitro andin vivo. inhibiting values which, against Eschcric/u'u (u/i.S[up/1ylocuc'cus uureus. Pseudo/norms urugiimxu and Proteus miruhilis.so significantly exceed that of the hitherto most effective commerciallyavailable urinary antiseptic. nitrofurantoin. that they represent avaluable advance in the art of medical practice, especially forcombating dangerous chronic infections of the urinary tract. forexample. pyelonephritis.

The new compounds (I) according to the present invention can beprepared. for example. by one of the following methods:

1. Reaction of the acid of the formula:

COOH

N l O N or of a reactive derivative thereof. with an amine of thegeneral formula:

(Ill

wherein R, has the same meaning as above.

2. Oxidativc cyclization ofa compound ofthe general formula:

c n L emu-mu- $-co-mi--n o n N in which R has the same meaning as above.

11 1mm CO-NH-R1 (v) wherein R has the same meaning as above.

4. Nitration of a compound of the general formula:

CO-NH-R wherein R, has the same meaning as above.

5. Treatment of a compound of the general formula:

I I OgiU- (F N-NR0 CO-NIb-R O N ---N 2 (VII) wherein R has the samemeaning as above. with an agent splitting off ammonia.

As derivatives of the acid of formula (ll), there can be used allcompounds which react with amines to give amides. Thus. for example, thenitrile can be converted into an amide directly or via an amidine. Inthe simplest case, there are used acid halides, especially acidchlorides, which can be obtained from the carboxylic acid by reactionwith a halogenation agent, for example, thionyl chloride or phosphorusoxychloride. Examples of other reactive derivatives include acid esters,for example the ethyl ester. and acid imidazolides. The reactiongenerally takes place easily in aqueous solvents and with good yields.The acid itself can be reacted with amines in the presence ofcarbodiimides.

The earboxylie acid (ll) used as a starting material can readily beobtained by hydrolysis of the corresponding nitrile which. in turn, isobtained by the oxidative cyclization of 6-cyano-3-[ 2-( 5-nitro-2-fufurylidene)-hydrazino]-pyridazine.

The oxidative cyclisation of the above-mentioned starting material. aswell as of the compounds (lV), can be carried out at a slightly elevatedtemperature, preferably in trifluoroacetic acid or glacial acetic acidor in a mixture thereof. Lead tetraacetate has proved to be especiallyuseful as oxidation agent.

The compounds of general formula (IV) can be readily obtained via thecorresponding nitrile or other reactive carboxylic acid derivative in amanner analogous to process 1.

For the condensation of the compounds (V) with 2-nitro-furan-S-carboxylic acid. the components can be simply heated in aninert. high boiling point solvent. for example diethylene glycoldimethyl ether. By the subsequent addition of water, rendering alkalineand extraction with an organic solvent. the products of the process canbe isolated.

The nitration of the compounds (VI) takes place in conventional manner,for example, with nitric acid and acetic anhydride in the cold. Thestarting materials (VI) can be obtained, for example, by the cyclisationof 6-cyano-3-( Z-furfuryIidene-hydrazino )-pyrida7.ine and reaction ofthe reaction product obtained therefrom, in a manner analogous toprocess 1.

The amidrazones of general formula (VII) used as starting materials canbe obtained by the condensation of -nitro-2-furan-imidoethers withappropriate 3- hydrazino-pyridazine derivatives. The cyelisation of thecompounds of general formula (VII) can be brought about simply byheating in an inert solvent. However, the splitting off of ammonia canalso be carried out by treating the amidrazones (VII) with aqueousmineral acids at ambient temperature or possibly with heating.

The nitriles used as precursors for compounds of the general formulae(II), (IV), (V), (VI) and (VII) can be obtained from the correspondinghalogen compounds in a manner analogous to Kolbes nitrile synthesis.Starting from the nitriles of the above-mentioned compounds, there arefirst obtained, by boiling in alcoholic hydrochloric acid, thecorresponding carboxylic acid esters which can then be saponified inaqueous formic acid, with the addition of methanesulphonic acid, to thecarboxylic acids.

The following Examples illustrate the preparation of the compounds ofthe present invention:

EXAMPLE 1 Preparation of 3-( 5-N itro-2-furyl)-6-carbamoyl-s-triazolo[4,3- b]pyridazine 0.147 g. 3-( 5-nitro-2-furyl)-6-chloroformyl-striazolo[4,3-blpyridazine was stirred for I hour atambient temperature with 1 ml. concentrated aqueous ammonia solution.Insoluble material was then filtered off with suction and washed withwater to give 0.1 g. 3-( 5-nitro-2-furyl )-6-carbamoyl-s-triazolo[4,3-b]pyridazine, which is recrystallized from 4 ml. dioxandimethylformamide (9:1 with the addition of charcoal. There was thus obtained0.06 g. 3-(5-nitro-2- furyl)-6-carbamoyl-s-triazolo[4,3-blpyridazine asa bright yellow product; m.p. 274 276C. (decomp).

The 3-( 5-nitro-2-fu ryl )-6-chloroformyl-s-triazolo- [4,3-b]pyridazineused as starting material was prepared as follows:

230 g. 3-chloro-6-cyano-pyridazine were suspended in 2500 ml. ethanol,198 ml. hydrazine hydrate were added, with cooling, at ambienttemperature and the reaction mixture was thereafter stirred for 30minutes at ambient temperature. The precipitated crystals were filteredoff with suction, washed with ethanol, triturated with a little icewater, filtered with suction and washed with ice water to give 195 g.crude 3-hydrazino- 6-cyano-pyridazine; m.p. l86 192C.

19.5 g. 3-hydrazino-6-cyano-pyridazine were dissolvedin 365 ml. waterand 192 ml. methanol, with heating. At 50C., there were added 20 ml. 2Nhydrochloric acid and a solution of 22.3 g. S-nitrofuran-Z- aldehyde in192 ml. methanol, followed by stirring for minutes at this temperatureand then for 30 minutes at ambient temperature. The solid material wasthen filtered off with suction, washed with 5071 aqueous methanol andthereafter with ether. There were thus obtained 35.17 g. crude6-cyano-3-l2-(5-nitro-2-furfurylidenc)-hydrazino]-pyridazine, which isboiled for 4 15 minutes with 220 ml. dioxan: after filtering off withsuction at 50C., there were obtained 23.6 g. of the pure compound; m.p.275 278C (decomp).

23.6 g. 6-cyano-3-[2-(5-nitro-2-furfurylidene)- hydrazinol-pyridazine(m.p. 275 278C. (decomp)) were dissolved in 320 ml. hot trifluoroaceticacid, diluted with 320 ml glacial acetic acid and 46.5 g. leadtetracetate introduced portionwise, at a temperature between 45C. and50C., while stirring. The reaction mixture was then further stirred for30 minutes at 50C., the small amount of undissolved material was quicklyfiltered off with suction and the filtrate was gently evaporated in avacuum. The evaporation residue was triturated with ice water, therebeing obtained 19.7 g. crude 3-( 5-nitro-2-furyl)-6-cyano-striaz0Io[4,3-blpyridazine; m.p. 186 190 198C. Afterrecrystallization from isopropanoldioxan (1:1), with the addition ofcharcoal, the compound melts, with decomposition, at 212 214C.

15.8 g. 3-(5nitro-2-furyl)-6-cyano-s-triazolo-[4,3- bjpyridazine wereboiled under reflux with 369 ml. 19% ethanolie hydrochloric acid for 2hours, then left to stand overnight at ambient temperature. 1.7 g. ofsolid material were then filtered off with suction and the filtrateevaporated to dryness in a vacuum. The evaporation residue wasintroduced portionwise in a saturated aqueous solution of sodiumbicarbonate and the precipitated product was filtered off with suction,washed with water and recrystallized from 350 ml. dioxan-ethanol (6:4),whereby 6.4 g. 3-(5-nitro-2-furyl- 6-ethoxy-carbonyI-s-triazolo 4 3-bpyridazine we re obtained; m.p. 225228C.

For the purpose of saponification, this carboxylic acid ester was nowboiled under reflux for 2 hours with 21.2 ml. 90% aqueous formic acid,to which 2 g. methane sulphonic acid had been added, a further 1 ml.methane sulphonic acid was then added thereto and reflux boilingcontinued for a further 2 hours. After cooling, the reaction product,i.e., the free carboxylic acid was precipitated out by the addition ofwater, filtered off with suction and washed with water. There were thusobtained 5.5 g. crude3-(5-nitro-2-furyl)-6-carboxy-s-triazolo-[4,3-b]pyridazine (m.p. 268273C.) which, after recrystallization from dioxan-dimethyl formamide (9:1 with the addition of charcoal, melts, with decomposition, at 280-282C.

The 3-( 5-nitro-2-furyl )-6-carboxy-s-triazolo[ 4,3-blpyridazine thusobtained was boiled under reflux for 8 hours with 55 ml. thionylchloride. The solution was then evaporated to dryness and the residuethoroughly triturated with trichlorocthylene. There were thus obtained5.6 g. 3-(5-nitro-2-furyl)-6'chloroformyl-striazolol4,3-blpyridazinewhich, in contradistinction to the free acid, is readily soluble indioxan.

EXAMPLE 2 Preparation of 3-( 5-Nitr r2-furyl )-6-( N-n-butylcarbamoyl)-striazolo[ 4,3-b pyridazinc 0.88 g. crude3-(5-nitro-2-furyl)-6-chloroformyl-striazolo|4,3-b]pyridazine wasstirred at ambient temperature for 1 hour with 11 ml. 6'71 aqueousn-butylamine solution. The reaction product was then filtered off withsuction, washed with water and recrystallized from 18 ml. aqueousmethanol, with the addition of charcoal, to give 0.55 g.3-(5-nitro-2-furyl)-6-(N-nbutyl-carbamoyl )'-s-triazolo[ 4.3-b]pyridazine in the form of a yellowish-white substance; nip. l56 157C.

EXAMPLE 3 Preparation of. 3-( 5-Nitro-2-furyl )-6-( N-allylcarbamoyl)-striazolo[ 4.3-b pyridazine 0.8 g.3-(5-nitro-furyl)6-chloroformyIs-triazolo- [4.3-b]pyridazir*e wasintroduced, with stirring. into a 67! aqueous solution of allylamine,stirring was continued for 1 hour at ambient temperature and the solidsubstance was then filtered off with suction. washed with water andrecrystallized from 85 ml. 80% aqueous methanol, with the addition ofcharcoal, there being obtained 0.42 g3-(5-nitro-2-furyl)-6-(N-allylcarbamoyl)-s-triazoIo[4.3-blpyridazine inthe form of a yellow product; m.p. I83 [85C.

The baeteriostatie activity of the compounds in accordance with theinvention was evaluated in vitro and in vivo. The following comparisoncompound and compounds according to the invention were used in thetests:

Compound No. Chemical Name A N-( S-Nitrofuryliden 1 -amino- (Comparisonhydantoine (sold under the Compound) trade name Furadantin" by NorwichPharmacal Co.) l 3-( S-Nitro-Z-furyl )-6-carhamoyl-s-triazolol 4.3-hpyridazinc 3-( S-Nitro-Z-furyl )-6-( N-nbutyI-carhamoyl )-s-tr'iazolo-14.3-b lpyridaiine 3 3-(S-Nitro-Z-furyU-fi-(N- allylcarbamoyl)-s-tria1olo- I 4.3-h lpyridazinc The absolute bacteriostatic minimalconcentration in vitro of the test compounds, for six differentbacterial species. is set out in micrograms of test compound permilliliter in the following Table I.

In addition the compounds were evaluated with respect to theirbacteriostatic activity in the excreted urine of rats following oraladministration. The results of these experiments are set out in TableII. The bacteriostatie maximum dilution of urine against Escherichiacoli I06) was determined 22 hours after 20 milligrams of test compoundper kilogram of body weight had been orally administered to the rats.Six (nine) rats were employed for each experiment (test compound); thetest results are calculated on the basis of 50(75) milliliter urinesamples. Each value reported represents the result of one experiment andis expressed in terms of the volumes of water with which one volume ofthe excreted urine sample could be diluted and still retain itsbacteriostatic property, due to the presence of test compoundv TABLE 11Maximum Bacteriostatic Dilution Volume Ratio) Compound No.

The compoundsof this invention are anti-microbials and have been foundto be bactericidal to the pathogens found in surface infections, gramnegative as well as gram positive. They additionally have utility asagents for routine treatment of acute and chronic bacterial infectionsof the urinary tract, including those caused by Proteus ap. Further theylend themselves because of their properties to use in the prevention ortreatment of mixed surface infections or wounds, severe burns, cutaneousulcers, pyodermas osteomyelitis, preparation of wounds and burns forskin grafting and prevention of infection of grafts and donor sites.

The compounds of the invention can be employed in the form of aqueoussolutions or suspensions thereof, as for instance, in the form of an0.01 to 0.05 aqueous suspension or solution; in the form of solutions innonaqueous, hygroscopic liquid vehicles such as polyethylene glycol, forinstance 0.] 0.5% solutions in polyethylene glycol; incorporation into awater-soluble ointment-like base (concentration 0.1 0.5%) or in a powderbase composed for instance of water-soluble polyethylene glyeols(concentration 0.1 to 0.5%); or in a form suitable for ingestion. Thus,a preferred form is a tablet containing to 200 mg. of active compound.Depending on the conditions, symptomatic and laboratory responses 100 to400 mg. per day can be administered. Another preferred form for orallyadministering the compounds of the invention is in the form of asuspension thereof in a water miscible flavored gel. Such gel cancontain from 1 to I0 mg. of compound per cc.

The compounds (I) can be administered orally and parenterally inadmixture with a liquid or solid pharmaceutical diluent or carrier. Asan injection medium, it is preferable to use water which contains thestabilizing agents, solubilizing agents and/or buffers conventional forinjection solutions. Additives of this type include for example,tartrate and borate buffers, ethanol, dimethyl sulphoxide,complex-forming agents (for example ethylene-diamine-tetraacetic acid)and high molecular weight polymers (for example liquid polyethyleneoxide) for viscosity regulation. Solid carrier materials include, forexample starch, lactose. mannitol, methyl- TABLE l ABSOLI'TEBACTERIOSTATIC ACTIVITY IN VITRO (MINIMAL CONCENTRATION IN ug/ml)Compound Streptococcus Escherichia Escherichia Proteus ProteusPseudomonas- No. l'accalis I) coli l8) coli I06) Mirahilis(298)mirahilis(279) aeruginosa(7l A If X 4 256 I28 IZX l l.(l() (1.25 (1.03]2 l 2 cellulose, talc, highly dispersed silicic acid, high molecularweight fatty acids (for example stearic acid), gela tine, agar-agar,calcium phosphate. magnesium stearate, animal and vegetable fats andsolid high molecular weight polymers (for example polyethylene glyeols).Compositions suitable for oral administration can, if desired, alsocontain flavoring and/or sweetening agents. For external use, thecompounds (1) according to the present invention can also be used in theform of powders and salves; for this purpose, they are mixed, forexample, with powdered, physiologically compatible diluents or withconventional salve bases.

It will be understood that the specification and examples areillustrative but not limitative of the present invention and that otherembodiments within the spirit and scope of the invention will suggestthemselves to those skilled in the art.

What is claimed is:

1. A nitrofuryl-triazolo[4,3-bl-pyridazine-amide compound of the formulao n-m wherein R, is hydrogen dekyl, alkenyl, or alkynyl of from 2 to 5carbon atoms.

2. The compound as claimed in claim 1 wherein R, is hydrogen.

3. A compound as claimed in claim 1 wherein R, is alkyl of from 2 to 5carbon atoms.

4. A compound as claimed in claim 1 wherein R, is alkenyl of from 2 to 5carbon atoms.

5. A compound as claimed in claim 1 wherein R, is alkynyl of from 2 to 5carbon atoms having one triple bond.

1. A NITROFURYL-TRIAZOLO(4,3-B)-PYRIDAZINE-AMIDE COMPOUND OF THE FORMULA2. The compound as claimed in claim 1 wherein R1 is hydrogen.
 3. Acompound as claimed in claim 1 wherein R1 is alkyl of from 2 to 5 carbonatoms.
 4. A compound as claimed in claim 1 wherein R1 is alkenyl of from2 to 5 carbon atoms.
 5. A compound as claimed in claim 1 wherein R1 isalkynyl of from 2 to 5 carbon atoms having one triple bond.
 6. Thecompound as claimed in claim 1 designated3-(5-nitro-2-furyl)-6-carbamoyl-s-triazolo (4,3-b)pyridazine.
 7. Thecompound as claimed in claim 1 designated3-(5-nitro-2-furyl)-6-(N-n-butyl-carbamoyl)-s-triazolo(4,3-b)pyridazine.8. The compound as claimed in claim 1 designated3-(5-nitro-2-furyl)-6-(N-allylcarbamoyl)-s-triazolo(4,3-b)pyridazine.